In recent years the incidence of dengue fever epidemics has increased and transmission has tended to be established over a geographically expanding area, including French Polynesia. An increase in air transportation contributes to the diffusion of the dengue virus from Southeast Asia, a region considered to be a hyperendemic dengue zone, to the Pacific region. Presently, little is known about the role of the vector (Aedes aegypti) in the diffusion of the dengue fever virus. A study on the genetic structure of vector populations was conducted using allozyme polymorphism. This study showed a low level of genetic exchange between mosquito populations on different islands. It is concluded that the occurrence of dengue hemorrhagic fever in French Polynesia during the last few years was likely due to the dispersal of the dengue virus via viremic people rather than via infected vectors.